linux-kernel - Re: [PATCH v6 02/12] drivers: base: cacheinfo: setup DT cache properties early

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Message-ID: <65f78c99-8b86-0098-7ced-899840a4bf16@arm.com>
Date:   Tue, 16 Jan 2018 15:07:35 -0600
From:   Jeremy Linton <jeremy.linton@....com>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        hanjun.guo@...aro.org, lorenzo.pieralisi@....com,
        rjw@...ysocki.net, will.deacon@....com, catalin.marinas@....com,
        gregkh@...uxfoundation.org, viresh.kumar@...aro.org,
        mark.rutland@....com, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, jhugo@...eaurora.org,
        wangxiongfeng2@...wei.com, Jonathan.Zhang@...ium.com,
        ahs3@...hat.com, Jayachandran.Nair@...ium.com,
        austinwc@...eaurora.org, lenb@...nel.org, vkilari@...eaurora.org,
        morten.rasmussen@....com, Palmer Dabbelt <palmer@...ive.com>,
        Albert Ou <albert@...ive.com>
Subject: Re: [PATCH v6 02/12] drivers: base: cacheinfo: setup DT cache
 properties early

Hi,

On 01/15/2018 06:33 AM, Sudeep Holla wrote:
> On Fri, Jan 12, 2018 at 06:59:10PM -0600, Jeremy Linton wrote:
>> The original intent in cacheinfo was that an architecture
>> specific populate_cache_leaves() would probe the hardware
>> and then cache_shared_cpu_map_setup() and
>> cache_override_properties() would provide firmware help to
>> extend/expand upon what was probed. Arm64 was really
>> the only architecture that was working this way, and
>> with the removal of most of the hardware probing logic it
>> became clear that it was possible to simplify the logic a bit.
>>
>> This patch combines the walk of the DT nodes with the
>> code updating the cache size/line_size and nr_sets.
>> cache_override_properties() (which was DT specific) is
>> then removed. The result is that cacheinfo.of_node is
>> no longer used as a temporary place to hold DT references
>> for future calls that update cache properties. That change
>> helps to clarify its one remaining use (matching
>> cacheinfo nodes that represent shared caches) which
>> will be used by the ACPI/PPTT code in the following patches.
>>
>> Cc: Palmer Dabbelt <palmer@...ive.com>
>> Cc: Albert Ou <albert@...ive.com>
>> Signed-off-by: Jeremy Linton <jeremy.linton@....com>
>> ---
>>   arch/riscv/kernel/cacheinfo.c |  1 +
>>   drivers/base/cacheinfo.c      | 65 +++++++++++++++++++------------------------
>>   include/linux/cacheinfo.h     |  1 +
>>   3 files changed, 31 insertions(+), 36 deletions(-)
>>
>> diff --git a/arch/riscv/kernel/cacheinfo.c b/arch/riscv/kernel/cacheinfo.c
>> index 10ed2749e246..6f4500233cf8 100644
>> --- a/arch/riscv/kernel/cacheinfo.c
>> +++ b/arch/riscv/kernel/cacheinfo.c
>> @@ -30,6 +30,7 @@ static void ci_leaf_init(struct cacheinfo *this_leaf,
>>   		CACHE_WRITE_BACK
>>   		| CACHE_READ_ALLOCATE
>>   		| CACHE_WRITE_ALLOCATE;
>> +	cache_of_set_props(this_leaf, node);
> 
> This may be necessary but can it be done as later patch ? So far nothing
> is added that may break riscv IIUC.

Well I think you have a bisection issue where the additional information 
will disappear between this patch and wherever we put this code back in.

> 
> Palmer, Albert,
> 
> Can you confirm ? Also, as I see we can thin down arch specific
> implementation on riscv if it's just using DT like ARM64. Sorry if
> I am missing to see something, so thought of checking.
> 
> [...]
> 
>> diff --git a/include/linux/cacheinfo.h b/include/linux/cacheinfo.h
>> index 3d9805297cda..d35299a590a4 100644
>> --- a/include/linux/cacheinfo.h
>> +++ b/include/linux/cacheinfo.h
>> @@ -99,6 +99,7 @@ int func(unsigned int cpu)					\
>>   struct cpu_cacheinfo *get_cpu_cacheinfo(unsigned int cpu);
>>   int init_cache_level(unsigned int cpu);
>>   int populate_cache_leaves(unsigned int cpu);
>> +void cache_of_set_props(struct cacheinfo *this_leaf, struct device_node *np);
>>
> 
> IIUC riscv is the only user for this outside of cacheinfo.c, right ?
> Hopefully we can get rid of it.

Yes, it should be the only user. I spent some time looking at the other 
users of this code to assure that they weren't doing partial DT setups 
and then having the common code use the resulting DT nodes. Riscv was 
the only case I found like that and that behavior is fairly new.

I think that they are doing it that way in order to get the cache type 
setup earlier. (to work around problems like the one recently fixed for 
the NONE->UNIFIED node conversion).


> 
> Other than that, it looks OK. I will wait for response from riscv team
> do that these riscv related changes can be dropped or move to later
> patch if really needed.
> 
> --
> Regards,
> Sudeep
>